One of the most general methods for preparing substituted amidines (B), (B'), and (B") is from substituted (methylammonium) (also called substituted formiminium halides), represented by formulae (A), (A') and (A") with primary amines and ammonia ##STR1## or with secondary amines ##STR2## wherein R is a monovalent substituent selected from the group consisting of hydrogen, alkyl, aryl, aralkyl, alkaryl, cycloalkyl, alkenyl, cycloalkenyl and heterocyclic radical; R' and R" are monovalent organic radicals independently selected from the group consisting of alkyl, aryl, aralkyl, alkaryl, cycloalkyl, alkenyl, cycloalkenyl and heterocyclic radical; X is a monovalent substituent selected from the following radicals: --OP(O)Cl.sub.2 ; --OPCl.sub.4, --O--S(O)Cl, --O--S(O)--R, and --O--C(O)--R; Y is chlorine or bromine; and Z is a divalent organic radical completing a 4 to 8 membered cycloaliphatic ring and containing (i) from 2 to 6 carbon atoms or (ii) from 2 to 6 carbon atoms and one hetero atom selected from the group consisting of oxygen, sulfur and nitrogen with the proviso that no hetero atom is adjacent the nitrogen atom.
The processes are illustrated (a) in the book by P. A. S. Smith, Open Chain Nitrogen Compounds, Vol. 1, pp. 177-184 (1965), W. A. Benjamin, Inc., New York; (b) in the review article by R. L. Schriner and F. W. Neumann, in Chemical Reviews, Vol. 35, pp. 351-425 (1944); (c) Angewandte Chemie, Vol. 72, pp. 836-845 (1960) and in individual papers, such as (d) Chemische Berichte, Vol. 92, pp. 837-849 (1959). The yields, however, are only mediocre, usually between 40 and 70%, and drastic heating conditions (between 150.degree. and 180.degree. C.) are required to effect reactions with the more basic amines (as shown in reference (d), p. 839).